There have been many breakthroughs published on the internet including muscles made from flexible polymer ribbons constructed from chains of carbon, fluorine, and oxygen molecules (Yoseph Bar-Cohen@ www discover com/augustissue/breakbend bots html) Mo Shahinpoor makes his out of polyacrylonitrile, see www sciam com/explorations/050596explorationsbox4 html, and a polymer muscle consists of thin sheets wrapped into a cigarlike cylinder
Other types of (internet announced) polymer muscle are thin sheets wrapped into a cigarlike cylinder These polymers stretch when one side of a sheet is given a positive charge and the other a negative These charges cause each wrapped sheet to contract toward the center of the cylinder, and this construction forces the cylinder to expand lengthwise When the power supply is off, the rope relaxes These polymers can push, pull, and lift loads
SRI International is investigating artificial muscle for small robots using electrostrictive polymers The muscle has compliant electrodes on the surface of the polymer film, contracts in thickness and extends in length and width due to the electrostatic forces when a voltage is applied The polymer enhances the electrostatic force because of its dielectric constant The net result is a muscle with a large strain (>30%) and a large actuation pressure (0.21 MPa in silicon, 1.9 MPa in polyurethane) The performance of the artificial muscle is comparable to the natural muscle, but with higher efficiency and faster response Artificial muscle can be fabricated using spin coating, dipping, or casting Once the muscle is fabricated, it can also be folded or rolled to make the muscle actuator more compact The artificial muscle actuator shown in FIG. 2 uses a spin coated film which is first folded then rolled, followed by folding and to achieve 20 layers The active muscle for the actuator is 10 mm in length and 3 mm in diameter, and gives a maximum stroke of 1 mm and maximum force of 2 grams (2×104 uN) Its weight is approximately 0.1 grams
The ability to reduce the number of layers and increase the muscle material's strain, thereby greatly reducing the size of the active muscle actuator and/or increasing the stroke distance at a greater force are challenges not achieved in the prior art
This application is based upon subject matters described in earlier filed and copending related applications and patents (see Related Applications above) which are specifically incorporated herein by reference